Some subjects of image fusion based on wavelet transform are discussed. Firstly, the method of selecting wavelet bases in image fusion is proposed, and the principle and formula on phase adjustment are deduced. Secondly, a new fusion rule of high frequency channel is presented. Based on the rule, a series of experiments are made on PC. The experimental result indicates that the algorithm and fusion rule are very suitable for multi-resource image fusion, especially for multi-spectral image fusion.